See your wincmd.ini file, that's where plugins are defined, plugins are called in descending order from top to bottom see the packer plugin section in wincmd.ini, the first wcx is probably the one being used, to uninstall a plugin just delete it's line from wincmd.ini, it's much easier to use Alexey's great plugin manager
http://www.totalcmd.net/plugring/tc_plugman.html
there have been some issues with Total7zip and newer alpha versions of 7zip.dll, you didn't say what are the bugs, it could just be a damaged archive.